The present invention relates to a method for controlling sluggish heating and cooling systems of buildings which by themselves or in connection with heavy building construction react slowly to temperature changes, i.e., they have a high heat capacity. Heavy building construction in this context means constructive designs including heating surfaces of great mass, for example, floor heating systems in which heating elements are embedded in concrete, or steel-reinforced concrete ceilings which are operated as heating and cooling surfaces (German Patent 40 27 833). The sluggishness with respect to temperature changes is additionally compounded by the fact that in buildings of heavy construction, i.e., masonary walls and steel-reinforced ceilings, are provided with good insulating materials, as is more and more the case in modern construction. Depending on the sluggishness of the system, a couple of hours often go by before switching on or off the heating or cooling system is noticable within the building. The control of sluggish heating and cooling systems is therefore very difficult.
Methods for controlling sluggish heating systems, especially for floor heating systems of the aforementioned kind, are known. They turn on the heat-generating and heat-distribution means when the measured temperature within the heating system T.sub.actual, for example, at the heating surfaces, is smaller than the preset nominal temperature T.sub.Hnominal : EQU T.sub.actual &lt;T.sub.Hnominal
In these cases, the required temperature at the heating surfaces T.sub.Hnominal must be lower the higher the exterior temperature is. When this known relation is represented in a coordinate system (FIG. 1), wherein the abscissa represents the exterior temperature T.sub.E and the ordinate represents the corresponding nominal temperature T.sub.Hnominal, a connecting line of all required heating surface temperature T.sub.Hnominal which, for increasing exterior temperatures, is a descending curve, the so-called heating curve. In very well insulated buildings with very large heating surfaces the curve is very flat and can be approximated by a straight line.
The required temperatures at the heating surfaces however not only depend on the exterior temperatures, but also on the quality of the heat insulating materials and the required amount of external air for the building as well as on the kind and size of the heating and cooling surfaces.
These parameters determine the slope of the approximated straight line of the heating curve. The slope is smaller the better the heat insulation of the building.
It is also known that internal and solar heat gains displace this straight line within the coordinate system parallel upwardly or downwardly and thus reduce or increase the intercept which in FIG. 1 is indicated at b.sub.H.
The equation for the straight line of the heating curve is thus EQU T.sub.Hnominal =T.sub.E .times.a.sub.H +b.sub.H.
wherein
T.sub.Hnominal : is the required heating surface temperature depending on the exterior temperature, PA1 T.sub.E : is the measured exterior temperature, PA1 a.sub.H : is the selectable slope of the heating curve (flat curve for good heat insulation and/or for greater heating surfaces), PA1 b.sub.H : is the selectable value of the parallel displacement, i.e., the intercept (greater value for smaller internal and solar heat gains). PA1 Presumed Parameters:
It is known that the condition for switching on the heating means is fulfilled when EQU T.sub.actual &lt;T.sub.E .times.a.sub.H +b.sub.H.
In analogy, the cooling system is activated when the actual temperature surpasses the nominal cooling temperature T.sub.Knominal, whereby the nominal cooling temperature as a function of the external temperature can also be approximated as a straight line (FIG. 2). The parameters a.sub.K and b.sub.K can be, but must not be identical to the corresponding values for the heating curve a.sub.H and b.sub.H. In contrast to the heating operation, in which for a greater exterior temperature the room temperature is maintained approximately at a constant value, usually at 21.degree. C., during the cooling operation the temperature difference between the exterior temperature and the room temperature may not be too great in order to prevent the risk of catching cold for the users of the building. Accordingly, different slopes for the heating and cooling curves result, as is known in the prior art. In contrast to the heating operation in which the heating surfaces for the purpose of releasing heat must be at all times hotter than the room to be heated, during cooling operation the temperature of the cooling surfaces for the purpose of dissipating heat must always be below the temperature of the room to be cooled. Thus, the value for the intercept of the cooling curve must be smaller than the intercept of the heating curve, i.e., b.sub.K is smaller than b.sub.H.
It is furthermore known, as represented in FIG. 3 illustrating both heating and cooling curves from FIG. 1 and FIG. 2 for clarification, that an adjustable range for the exterior temperature exist which, in general, is between 12.degree. and 16.degree. C. in which the building is neither heated nor cooled. This neutral range can be preset and depends also on the temperature sluggishness and the internal and solar heat gains of the building.
As an example for the switching conditions for heating according to the prior art the following is presented:
Exterior temperature T.sub.E =+8.degree. C., PA2 Slope of the heating curve a.sub.H =-0.25 (i.e., when the exterior temperature drops by 4K., the heating surface temperature must be raised by 0.25.times.4K=1K.). PA2 Slope b.sub.H =+26K. (approximately true for great heating surfaces and good heat insulation).
From this the condition for switching on heating results as follows: EQU T.sub.actual &lt;+8.degree. C..times.(-0.25)+26K. EQU T.sub.actual &lt;+24.degree. C.
Such a known control however cannot prevent in sluggish systems that, for example, in a cool night the building is heated and the next day, when the sun is shining, the building is too hot. For the present conventional, somewhat less sluggish heating systems these controls may be sufficient. However, energy saving efforts have become increasingly more important and require improved and better heat insulation. Better insulation in connection with heavy building construction results in heated buildings requiring longer and longer cooling periods, respectively, the cooled building requiring increasingly longer heating periods. Heating and cooling systems accordingly react increasingly sluggish, independent of how reactive and fast the heating and cooling system alone would be. A control process according to the aforedescribed principle thus takes effect only after a certain period of time which depends on the sluggishness of the system.
It is therefore an object of the present invention to provide a method for controlling a sluggish heating and cooling system for buildings, which, due to a high heat capacity, reacts only sluggishly to temperature changes and whose nominal temperature is represented as a function of the exterior temperature, such that a heating or cooling process does not disfavorably take effect at a time later than the desired nominal time due to the sluggishness of the building, i.e., at a time when the heating or cooling effect is no longer needed.